THURSDAY, May 5 (HealthDay News) -- Children with autism have proteins in the blood as well as immune-system components that differ significantly from children without the disorder, researchers report.

If the findings are substantiated in larger studies involving more children, the research might one day lead to a diagnostic test for autism in infancy. Right now, the disorder can only be diagnosed by observing behavior and it can't be done reliably until a child is 2 to 3 years old, the researchers said.

The study was one of several presented Thursday that offer hope in the areas of diagnosing, treating and, possibly, preventing autism. The presentations were made at the Fourth International Meeting for Autism Research, in Boston.

Developing a blood test that could lead to earlier detection of the disorder would be invaluable for several reasons, said David Amaral, co-author of the study and research director at the University of California, Davis M.I.N.D. Institute.

Earlier diagnosis would allow for earlier treatment, during the time when a young child's brain is developing rapidly. Such a tool might also help prevent regressive autism, a type of autism that seems to occur when a child born vulnerable to the disorder is exposed to an environmental trigger, Amaral said.

"If one could detect at birth those children who are vulnerable and, at the same time, understand what it is in the environment that is the trigger, it would be possible to prevent the child from ever experiencing the trigger," Amaral said.

For this study, researchers took blood samples from 70 four-to-six year olds who had been diagnosed with autism and from 35 healthy children. Three levels of analysis were carried out on each sample: immune cells, proteins and small molecules, called metabolites.

"We found some very striking differences at all three levels," Amaral said. For instance, the number of antibody-producing B cells was increased by 20 percent in the autism group. "The immune system appears to be dysregulated, which provides some support for the notion that we should be spending more time and attention on immune factors" as contributors to autism, Amaral said.

"We're not at the stage of having a diagnostic marker," he cautioned. "It may be that none of the proteins that we now see as different are going to be that marker. But the study gives us confidence that this is a good strategy. This is a good strategy to pursue to ultimately develop a diagnostic marker."

Autism is a potentially devastating disorder generally diagnosed between the ages of two and four. Affected children can become withdrawn; in severe cases they are unable to communicate with their loved ones or any other aspect of the world around them.

For reasons unknown, there has been a rise in the prevalence of autism. The disorder now affects as many as one in 166 children in the United States.

The causes and, consequently, any hope for a cure for autism have remained elusive. It is becoming increasingly clear, however, that many factors probably contribute to the disorder.

A second study presented Thursday at the conference found that children with autism have different immune system responses than healthy children, a finding that might also contribute to advancing diagnostics and treatment for the disorder.

Researchers analyzed immune cells from blood taken from 30 children with autism and 26 healthy children, all aged two to five years. Then the scientists exposed the cells to bacterial and viral agents, including vaccine antigens, which typically unleash T-cells, B-cells and macrophages, all part of the immune system.

The immune responses of the autism group were clearly different from those of the healthy children, namely, there were lower levels of compounds called cytokines in the autism group.

"Cytokines are molecules that perform crosstalk between different cell types. They are important communicators," explained Judy Van de Water, co-author of the study and associate professor of rheumatology, allergy and clinical immunology at the University of Californnia, Davis School of Medicine and the UC Davis M.I.N.D. Institute. Among other things, cytokines affect sleep and many children with autism have sleep disorders.

"It's a long road for us to say what that immune dysfunction is and what role it may play. However, it does give us a good clue that there is something in these kids at the biological level," Van de Water said.

The authors stressed that the use of vaccine antigens in the study had nothing to do with controversial claims by some that childhood vaccinations cause autism. "At this point, it's something we can't confirm or deny regarding vaccines and autism," Van de Water said.

"Our findings at this point don't really debunk or provide support on whether vaccines are dysregulating the immune system," Amaral added.

Other findings being presented at the conference include:

Certain behaviors, some evident in the first year of life, seem to predict autism. Researchers have found differences in vocal abilities and very early language skills, among other things, in children who have older siblings with autism. They also observed differences in gesture and eye contact in the younger children, who had not yet been diagnosed with autism. These differences in high-risk very young children seemed to predict they would develop autism later.

Relatives of people with autism seemed to share certain traits, including large head size, abnormal brain processing of faces and difficulty in reading another person's mental state.

Rats exposed to PCBs had disturbances in certain regions of the brain. In humans, these disturbances would affect language development, which is a hallmark of autism. PCBs are compounds that were used as coolants and lubricants in certain electrical equipment because of their insulation ability. They were banned in the United States in 1977 due to concern over their health effects.

More information

The National Institute of Child Health and Human Development can tell you more about autism.

SOURCES: May 5, 2005 news conference with David G. Amaral, Ph.D., research director, University of California, Davis M.I.N.D. Institute and Judy Van de Water, Ph.D., associate professor of rheumatology, allergy and clinical immunology, University of California, Davis School of Medicine and UC Davis M.I.N.D. Institute; Fourth International Meeting for Autism Research, Boston